Male and female black swans form long and mostly enduring pair bonds that last for many years. However, if one of the pair dies, the widowed partner will generally find itself a new mate within six months or so. About one in twenty pairs also divorce – the male and female both survive but form new partnerships with other birds.
Even though pairs show strong social fidelity, a cob cannot always be sure that he is the father of all of the cygnets in his brood. A raft of recent studies has shown that infidelity is rife among birds, even in species where males and females form lifelong pair bonds. By taking small blood samples from swans as part of the routine capture procedure, we have been able to assess patterns of paternity by analysing their DNA. It turns out that about 15 per cent of all cygnets are not sired by their social ‘father’, but by another cob in the population.
Posted in: Black swans